[marcoallegretti]

Summary

This adds an initial CI baseline for pull requests and pushes to main.

The workflow provides separate results for:

• Rust formatting;
• Rust workspace compilation and tests;
• TypeScript type checking and tests;
• documentation type checking and builds;
• Nix flake evaluation.

The Rust job uses the development environment pinned by flake.lock, prepares /tmp/.X11-unix with the permissions expected by the socket tests, and caches Cargo downloads and build artifacts using the Rust and Nix dependency state.

The development shell now also provides a fontconfig fallback. This was necessary because the text-rendering tests depend on a discoverable default font and otherwise fail on minimal environments. The fallback is supplied by nixpkgs and does not change the public API or packaged runtime.

Validation

The following checks pass:

• cargo fmt --all -- --check
• cargo test --workspace --all-targets --locked --no-run
• cargo test --workspace --all-targets --locked
• npm run typecheck
• npm run test:overlays
• npm run test:output-power
• documentation type checking and production build
• nix flake check --no-build

The Rust workspace result is 404 passed and 4 ignored. The ignored tests remain explicitly marked as requiring surfaceless EGL or OpenGL ES.

The build still reports two existing irrefutable_let_patterns warnings in the scene3d tests. This PR does not broaden its scope to address them.

Scope

This intentionally does not add strict Clippy enforcement, hardware-dependent compositor tests, Nix package builds, or cross-architecture execution. Those can be evaluated separately once the baseline produces real CI timing and cache data.

API impact

No API break.

Part of #152.

[bea4dev]

thanks! LGTM!